The invention relates to a bearing arrangement for the armature shaft of an electric motor mounted in a support frame. The bearing arrangement according to the invention is especially applicable to electric motors mounted in portable electric tools such as drills and the like.
In tools of this type, the supporting forces of the armature shaft act directly against the bearing surface of the sleeve bearing engaging the shaft. This contact is on a very large area and because of a misalignment of the shaft with respect to the sleeve bearing, friction occurs which generates a great quantity of heat that is generally dispersed through the supporting structure. However, such operating inevitably reduces the efficiency of the motor substantially.
It is known that the support for receiving the thrust can be arranged at the end of the armature shaft and that the thrust can act on a spherical component mounted on the rotational axis of the armature shaft. However, in the known arrangement, it is very difficult to maintain the co-axial alignment of the sphere with the axis of rotation of the shaft and this results in lateral forces acting on the sleeve bearing. Such lateral forces develop when there is a misalignment between the sleeve bearing and the shaft.